1. Field of the Invention
This invention relates to an ion laser tube and in more particular to an ion laser tube having a ceramic capillary member with a high laser power being obtained due to discharge of a large electric current.
2. Description of the Related Art
Generally, in case of ion laser tubes in which laser oscillation is generated by transition between energy levels of ionized gas obtained due to ionization of a gaseous active medium such as argon, krypton or the like, ion density musk be increased in order to obtain a high laser power. To this end, it is sometimes necessary to apply a large electric current of not less than 30 amperes to a discharge path in a capillary member. Therefore, it has been required that a plasma capillary member and an envelope are made of a high thermal conductivity material which is capable of efficiently removing heat generated in the plasma capillary member due to the large electric current, and further that the material for the capillary member has a good durability to high ion density.
Recently, silicon carbide (SIC) and aluminum nitride (A1N) have been used as materials of satisfying the requirements as mentioned above.
Referring now to FIG. 1, which shows a longitudinal section of a conventional ion laser tube, the ion laser tube has a plurality of incorporated capillary members 17 each having a flanged SiC capillary member 1 with a central hole 2 for an electric discharge path and an A1N envelope 6 in which the capillary member 1 is accommodated or incorporated, the envelope 6 being provided with a plurality of gas return holes 5 and being constructed at the same angular intervals to surround the central hole 2, and the capillary member 1 and the envelope 6 being bonded and secured to each other by solder glass such as fritted glass 7. The plurality of incorporated capillary members 17 are coaxially arranged along a capillary axis of the ion laser tube and in series connected and secured to one another by using an appropriate implement (not shown) and fritted glass 9. The capillary members 1 are spaced apart from each other. An end of a cylindrical borosilicate glass member 10 is connected and secured to each end of the outermost capillary members 17. Furthermore, each of a pair of metal dishes 13 equipped with an anode electrode 11 and a cathode electrode 12, respectively, is connected and secured to the other end of each borosilicate glass member 10 and a Brewster window 14 is secured to a tip end of a tubular member 19 at an angle inclined to the laser capillary axis, the tubular member 19 extending outwardly from a central portion of each metal dish 13. And the ion laser tube is completed by sealing a prescribed amount of argon gas therein. The gas is charged and exhausted through a metal tube 18.
The above-mentioned ion laser tube and its modifications are taught in U.S. Pat. No. 4,912,719, the disclosure of which is hereby incorporated by reference herein.
In the above-mentioned conventional ion laser tube, however, the SiC capillary member is easily sputtered by electric discharge and thus the composition thereof deviates from stoichiometric composition (SiC=1:1). Consequently, there is an obstacle that the laser power is sharply lowered and has a short life.
Furthermore, it is very difficult to make the SiC member having the stoichiometric composition because of variation in manufacture.